1. Field of the Invention
This invention relates to automatic lathes for shaping multiple cams all disposed on the same shaft, such as the lathes used for the production of camshafts of internal combustion engines.
2. Description of the Prior Art
Cam turning usually precedes a truing step and requires double guiding of the tool, which must move radially to produce the cam profile and angularly in the cutting plane to give a constant cutting angle whatever the cam profile may be, the tool axis being continuously oriented along the profile radius passing through the tool tip. These complex movements are usually produced by cams which act simultaneously on tool slide movements by wasy of a mechanical transmission comprising levers and slideways.
In some lathes of this kind the workpiece, if a camshaft, is retained conventionally between centers and the cams are machined simultaneously through the agency of a group or set of tool slides, the cams which provide axial and radial guiding of the tool slides being respectively disposed on two parallel shafts; the camshaft to be machined is in this case borne by its bearing surfaces being cradled in support members, to obviate bending of the camshaft.
The master guide cams must be disposed near the tool, to ensure that the motion is transmitted with adequate rigidity, and are usually to a multiple scale of the cams of be machined, for improved accuracy and for improved stiffness of the shafts bearing the cams, such shafts being subject to the bearing reactions of the tool slides during cutting. The resulting guide-camshafts are bulky, and their nearness to the tool restricts access to the tool slides and makes it difficult to supply and remove workpieces in automatic cycles. The restricted accessibility also hampers swarf removal, since the swarf may jam between the cams and the rollers and thus cause damage and rejects, so that it is difficult to produce long runs.